Cell Structure

Microvilli and cilia are cell structures.

Describe how the structure of cilia differs from the structure of the microvilli visible in Fig. 2.1 and Fig. 2.2.

A scientist measured the length and the diameter of some of the microvilli shown in Fig. 2.1 to estimate the total surface area of microvilli on the surface of the epithelial cell.

The scientist assumed that each microvillus was cylindrical in shape.

Suggest one other measurement needed to estimate the total surface area of the microvilli of the epithelial cell.

Identify the organelle labelled Z in Fig. 2.1 and explain why there is a large number of these organelles in the epithelial cells of the small intestine.

organelle ______

explanation ______

Bacteria are found attached to epithelial cells in the intestines of mammals.

Describe how the organisation and distribution of DNA in epithelial cells differs from the organisation and distribution of DNA in bacterial cells.

With reference to Fig. 4.1, outline the similarities and differences between the outer membrane of a Gram-negative bacterial cell and the cell surface membrane of a eukaryotic cell.

With reference to Fig. 4.2, suggest why fewer O-IMVs are formed than OMVs.

Suggest why ATP is found within O-IMVs but not in OMVs.

Suggest and explain why the discovery that O-IMVs contain DNA has implications for antibiotic resistance.

Animal cells, plant cells and prokaryotic cells have similarities and differences in their structure.

Table 1.1 lists five organelles found in cells.

Complete Table 1.1 by placing a tick (✓) to show whether the organelle is present in animal cells, plant cells and prokaryotic cells or a cross (✗) if the organelle is absent.

Put a tick (✓) or a cross (✗) in every box.

The first row has been completed for you.

Table 1.1

Name the structures labelled P.

Explain how the organelle labelled Q in Fig. 1.1 is involved in this process.

The structures labelled A and B on Fig. 1.1 are sections of two mitochondria.

Suggest why A and B are different shapes.

The structure labelled D on Fig. 1.1 is a mitochondrion about to divide.

Explain the importance of the division of mitochondria for the cell shown in Fig. 1.1 and for cells in the root tips of thale cress.

Within a cell, substances move between the nucleus and the cytoplasm. The area labelled C in Fig. 1.1 shows an area where this communication occurs.

Make a large, labelled drawing of area C to show where this communication occurs.

Outline the functions of the nucleus in non-dividing cells, such as the cell in Fig. 1.1.

Each of the statements A to D describes a structure found in eukaryotic cells.

Identify the structure that is described in each statement.

A An organelle that contains 70S ribosomes.

______

B A thread-like structure composed of DNA and histone proteins.

______

C The organelle that modifies and packages proteins for secretion.

______

D The structure that synthesises rRNA and combines it with proteins.

______

Prokaryotes and plant cells have cell walls.

Outline the composition of the cell wall of a prokaryote and the composition of the cell wall of a plant cell to show how they differ.

Calculate the actual width of the organelle labelled A, as shown by line X–Y.

State the formula that you will use and show your working.

Give your answer in µm and to one decimal place.

actual width = ______ $\text{µm}$

Name the organelle A and state its role in cells.

name = ______

role = ______

Name the cell structure labelled B and state one reason for your answer.

name = ______

reason = ______

The actual diameter of the nucleus between X and Y is $9.0\ \text{µm}$.

Calculate the magnification of the plant cell shown in Fig. 2.1.

Write down the formula for magnification and use it to make your calculation. Show your working.

formula

magnification $\times$ ______

Describe the structure of a nucleus.

State the function of mitochondria.

Name structure A.

Calculate the magnification of the image in Fig. 1.1.

Show your working.

magnification $\times$ = ______

Explain why the light microscope could not be used to produce the image in Fig. 1.1.

Scientists think that mitochondria were once prokaryotes. The evidence for this is that mitochondria have features in common with prokaryotes.

State two features that mitochondria have in common with prokaryotes.

1. ______

2. ______

State the name of the organelles described.

Suggest one reason why the organelles described do not always seem to have the same shape.

State the name of the cell structures described.

Draw a circle around the measurement that has the same value as $25\ \text{nm}$.

$0.00025\ \text{µm}$      $0.0025\ \text{µm}$      $0.025\ \text{µm}$      $0.25\ \text{µm}$      $2.5\ \text{µm}$

State the name of the cell structures described.

Explain one advantage to the plant cell of having these structures.

Fig. 1.1 is a transmission electron micrograph of part of an epithelial cell from the small intestine of a mammal.

Name the cell structures labelled X in Fig. 1.1 and state their function.